Line distance protection near unconventional energy sources

This paper introduces distance elements suitable for protecting lines near wind-turbine generators and inverter-based sources. The paper begins by analyzing issues with distance elements that use memory polarization for directionality and negative-sequence current for faulted-loop selection and reactance comparator polarization. The analysis is based on worst-case assumptions derived from field cases and published findings, it avoids modeling by using proprietary and uncertain information about the sources, and it does not assume that the source fault response complies with any local, international, present, or pending interconnection standards. The paper identifies parts of the distance element logic that do not work well in applications near unconventional sources and replaces the problematic parts with alternatives that perform satisfactorily. The solution is based on an offset distance characteristic to avoid memory polarization. It further uses separate directional elements to directionalize the offset distance elements by taking advantage of the system fault current contribution rather than the source current contribution.